/** * Copyright (c) 2021 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include "pico/stdlib.h" #include "pico/binary_info.h" #include "hardware/gpio.h" #include "hardware/i2c.h" /* Example code to talk to an MPL3115A2 altimeter sensor via I2C See accompanying documentation in README.adoc or the C++ SDK booklet. Connections on Raspberry Pi Pico board, other boards may vary. GPIO PICO_DEFAULT_I2C_SDA_PIN (On Pico this is 4 (pin 6)) -> SDA on MPL3115A2 board GPIO PICO_DEFAULT_I2C_SCK_PIN (On Pico this is 5 (pin 7)) -> SCL on MPL3115A2 board GPIO 16 -> INT1 on MPL3115A2 board 3.3v (pin 36) -> VCC on MPL3115A2 board GND (pin 38) -> GND on MPL3115A2 board */ // 7-bit address #define ADDR 0x60 #define INT1_PIN _u(16) // following definitions only valid for F_MODE > 0 (ie. if FIFO enabled) #define MPL3115A2_F_DATA _u(0x01) #define MPL3115A2_F_STATUS _u(0x00) #define MPL3115A2_F_SETUP _u(0x0F) #define MPL3115A2_INT_SOURCE _u(0x12) #define MPL3115A2_CTRLREG1 _u(0x26) #define MPL3115A2_CTRLREG2 _u(0x27) #define MPL3115A2_CTRLREG3 _u(0x28) #define MPL3115A2_CTRLREG4 _u(0x29) #define MPL3115A2_CTRLREG5 _u(0x2A) #define MPL3115A2_PT_DATA_CFG _u(0x13) #define MPL3115A2_OFF_P _u(0x2B) #define MPL3115A2_OFF_T _u(0x2C) #define MPL3115A2_OFF_H _u(0x2D) #define MPL3115A2_FIFO_DISABLED _u(0x00) #define MPL3115A2_FIFO_STOP_ON_OVERFLOW _u(0x80) #define MPL3115A2_FIFO_SIZE 32 #define MPL3115A2_DATA_BATCH_SIZE 5 #define MPL3115A2_ALTITUDE_NUM_REGS 3 #define MPL3115A2_ALTITUDE_INT_SIZE 20 #define MPL3115A2_TEMPERATURE_INT_SIZE 12 #define MPL3115A2_NUM_FRAC_BITS 4 #define PARAM_ASSERTIONS_ENABLE_I2C 1 volatile uint8_t fifo_data[MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE]; volatile bool has_new_data = false; struct mpl3115a2_data_t { // Q8.4 fixed point float temperature; // Q16.4 fixed-point float altitude; }; void copy_to_vbuf(uint8_t buf1[], volatile uint8_t buf2[], uint buflen) { for (size_t i = 0; i < buflen; i++) { buf2[i] = buf1[i]; } } #ifdef i2c_default void mpl3115a2_read_fifo(volatile uint8_t fifo_buf[]) { // drains the 160 byte FIFO uint8_t reg = MPL3115A2_F_DATA; uint8_t buf[MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE]; i2c_write_blocking(i2c_default, ADDR, &reg, 1, true); // burst read 160 bytes from fifo i2c_read_blocking(i2c_default, ADDR, buf, MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE, false); copy_to_vbuf(buf, fifo_buf, MPL3115A2_FIFO_SIZE * MPL3115A2_DATA_BATCH_SIZE); } uint8_t mpl3115a2_read_reg(uint8_t reg) { uint8_t read; i2c_write_blocking(i2c_default, ADDR, &reg, 1, true); // keep control of bus i2c_read_blocking(i2c_default, ADDR, &read, 1, false); return read; } void mpl3115a2_init() { // set as altimeter with oversampling ratio of 128 uint8_t buf[] = {MPL3115A2_CTRLREG1, 0xB8}; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // set data refresh every 2 seconds, 0 next bits as we're not using those interrupts buf[0] = MPL3115A2_CTRLREG2, buf[1] = 0x00; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // set both interrupts pins to active low and enable internal pullups buf[0] = MPL3115A2_CTRLREG3, buf[1] = 0x01; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // enable FIFO interrupt buf[0] = MPL3115A2_CTRLREG4, buf[1] = 0x40; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // tie FIFO interrupt to pin INT1 buf[0] = MPL3115A2_CTRLREG5, buf[1] = 0x40; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // set p, t and h offsets here if needed // eg. 2's complement number: 0xFF subtracts 1 meter //buf[0] = MPL3115A2_OFF_H, buf[1] = 0xFF; //i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // do not accept more data on FIFO overflow buf[0] = MPL3115A2_F_SETUP, buf[1] = MPL3115A2_FIFO_STOP_ON_OVERFLOW; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); // set device active buf[0] = MPL3115A2_CTRLREG1, buf[1] = 0xB9; i2c_write_blocking(i2c_default, ADDR, buf, 2, false); } void gpio_callback(uint gpio, __unused uint32_t events) { // if we had enabled more than 2 interrupts on same pin, then we should read // INT_SOURCE reg to find out which interrupt triggered // we can filter by which GPIO was triggered if (gpio == INT1_PIN) { // FIFO overflow interrupt // watermark bits set to 0 in F_SETUP reg, so only possible event is an overflow // otherwise, we would read F_STATUS to confirm it was an overflow printf("FIFO overflow!\n"); // drain the fifo mpl3115a2_read_fifo(fifo_data); // read status register to clear interrupt bit mpl3115a2_read_reg(MPL3115A2_F_STATUS); has_new_data = true; } } #endif void mpl3115a2_convert_fifo_batch(uint8_t start, volatile uint8_t buf[], struct mpl3115a2_data_t *data) { // convert a batch of fifo data into temperature and altitude data // 3 altitude registers: MSB (8 bits), CSB (8 bits) and LSB (4 bits, starting from MSB) // first two are integer bits (2's complement) and LSB is fractional bits -> makes 20 bit signed integer int32_t h = (int32_t) buf[start] << 24; h |= (int32_t) buf[start + 1] << 16; h |= (int32_t) buf[start + 2] << 8; data->altitude = ((float)h) / 65536.f; // 2 temperature registers: MSB (8 bits) and LSB (4 bits, starting from MSB) // first 8 are integer bits with sign and LSB is fractional bits -> 12 bit signed integer int16_t t = (int16_t) buf[start + 3] << 8; t |= (int16_t) buf[start + 4]; data->temperature = ((float)t) / 256.f; } int main() { stdio_init_all(); #if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN) #warning i2c / mpl3115a2_i2c example requires a board with I2C pins puts("Default I2C pins were not defined"); return 0; #else printf("Hello, MPL3115A2. Waiting for something to interrupt me!...\n"); // use default I2C0 at 400kHz, I2C is active low i2c_init(i2c_default, 400 * 1000); gpio_set_function(PICO_DEFAULT_I2C_SDA_PIN, GPIO_FUNC_I2C); gpio_set_function(PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C); gpio_pull_up(PICO_DEFAULT_I2C_SDA_PIN); gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN); gpio_init(INT1_PIN); gpio_pull_up(INT1_PIN); // pull it up even more! // add program information for picotool bi_decl(bi_program_name("Example in the pico-examples library for the MPL3115A2 altimeter")); bi_decl(bi_1pin_with_name(16, "Interrupt pin 1")); bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C)); mpl3115a2_init(); gpio_set_irq_enabled_with_callback(INT1_PIN, GPIO_IRQ_LEVEL_LOW, true, &gpio_callback); while (1) { // as interrupt data comes in, let's print the 32 sample average if (has_new_data) { float tsum = 0, hsum = 0; struct mpl3115a2_data_t data; for (int i = 0; i < MPL3115A2_FIFO_SIZE; i++) { mpl3115a2_convert_fifo_batch(i * MPL3115A2_DATA_BATCH_SIZE, fifo_data, &data); tsum += data.temperature; hsum += data.altitude; } printf("%d sample average -> t: %.4f C, h: %.4f m\n", MPL3115A2_FIFO_SIZE, tsum / MPL3115A2_FIFO_SIZE, hsum / MPL3115A2_FIFO_SIZE); has_new_data = false; } sleep_ms(10); }; #endif }

This firmware image was imported from the pico-examples repository. 


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